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Title: Steric acceleration of intramolecular cyclisations
Author: Smith, Graham
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2004
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The promotion of intramolecular cyclisations using various synthetic methodologies remains an area of considerable interest in organic chemistry. In this thesis, the potential for large, bulky groups ("steric buttresses") to promote intramolecular cyclisations by a combination of entropic and enthalpic factors is presented. For the purposes of this study both Diels-Alder and ene cyclisations have been studied. The use of steric buttresses to promote the ene cyclisation of a 1,7-diene under relatively mild conditions is described, with different buttressing groups attached, to enable comparison of their relative buttressing ability. In this series the thermal stability of the cyclic products was also investigated, thus allowing further conclusions to be drawn on the buttressing ability of the groups studied. The ene reaction of a range of 1,6-dienes to give substituted pyrrolidines was investigated. This has enabled comparisons to be made on the reactivity of the enophiles in question. More importantly, the relative buttressing ability of the buttresses studied has been assesseda, llowing their ability to both promote cyclisation and control selectivity to be classified. In addition our efforts to develop a viable synthetic route to kainic acid are discussed. The thermolysis of 1,6-dienes incorporating a hetero-enophile component was also the subject of study. The enophiles in this case ranged from carbonyl compounds to their imino and nitrile counterparts. Once again, this has enabled conclusions to be drawn on the reactivity of the enophiles involved. In addition, these studies have allowed us to better understand the suitability of steric buttressing as an aid to intramolecular cyclisations. Finally, in an effort to develop a chiral steric buttressing methodology, the use of ß-cyclodextrin ("macrocyclic steric buttressing") to promote an intramolecular Diels- Alder cyclisation is discussed. This study also resulted in the discovery of a remarkable solvent effect for an intramolecular, pericyclic reaction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available